In general, a motor for a washing machine includes a rotor and a stator. The stator includes a stator core in which a number of steel sheets are laminated on top of each other and an insulator surrounding the stator core. Such a structure of the stator is disclosed in U.S. Pat. Nos. 7,336,014 and 7,362,028 and U.S. Patent Publication No. 2011/0036127.
In U.S. Pat. No. 7,336,014, the stator has a structure that an upper insulator and a lower insulator which come in contact with each other and surround nearly all of the inner circumferential surface of a stator core. Such a structure may generate noise by a fine vibration near the boundary of the two insulators when a motor is operated, and require relatively lots of resin molding because the insulators cover most of the inner circumference of the stator core.
In U.S. Pat. No. 7,362,028, because a fastening part is formed by the upper insulator and the lower insulator which come into contact with each other, the problems of vibration, noise and increase of manufacturing costs are not solved. Moreover, one or more fastening projections protrude inwardly from a hole of the connected part, but in this instance, the fastening projection is cut out by a sleeve when the sleeve is forcedly pressed, and hence, it generates foreign matters.
In U.S. Patent Publication No. 2011/0036127, a fastening part is formed only at the upper insulator and is not formed at the lower insulator, but such a structure is weak in fastening strength because only one insulator is fastened to the stator core. Furthermore, such a structure also does not solve the problems of the fine vibration and noise.
Therefore, in order to solve the above problems, the inventors of the present invention propose a new structure of a stator of a motor for a washing machine.